This invention is directed to construction instruments, and more particularly to a method and apparatus for laying out imaginary guide lines for masonry, carpentry, steel electrician, pipe fitters, or other types of construction work. During various stages of construction it is often necessary to lay out an imaginary line along which a wall, edge, or other structural element of the construction is desired to follow. This is often accomplished by laying out a cord or string along the desired path. Sometimes the desired path is a horizontal, as in the case of the top of a wall or masonry foundation (line level). Other examples might be an angular extending edge of a roof or other structural element.
A significant problem exists at this time in trying to extend the cord along the desired angle, as there is no existing structural member against or on top of which a level or other simple construction instrument can be placed to ensure the correctness of the angle, and more complex instruments are required. Often it is desired to periodically check the guide cord to make sure it is still accurately positioned, and where complex instruments were initially used, they must be set up again. Therefore, there is a need for some type of simple instrument that can be used in cooperation with a guide cord to determine when the cord is at the proper angle or attitude.
The present invention, then, is directed to such a simple instrument which generally includes a protractor-like instrument having a lip or suspension means along one edge of the base portion thereof, by means of which the protractor-like instrument can be suspended from the cord. In combination with this protractor-like instrument, a plumb bob is suspended from the center point of the protractor scale.
Thus, when the protractor is suspended from the cord by the lip, the position on the protractor scale to which the plumb bob is directed is indicative of the attitude or angle from the horizontal at which the guide cord lies. By adjusting the guide cord until the plumb bob points to the desired angle, the cord may be properly laid out.
As an additional feature there is provided a pivotally activated locking mechanism which, in conjunction with the lip, engages the cord and prevents the instrument from sliding when the cord is extended to extreme angles.
There is thus provided a construction instrument for laying out a projected angular course from a known point at a prescribed angle.
Another object of the present invention is to provide an instrument of the type described which may be utilized even in the absence of a structural element against which a straight edge of the instrument may be positioned.